Yep, its extremely stange, Sonic Reel DVD which costs around $500 can not do multiangles yet a $199 program can, it beats me... I guess Sonic will soon realize (I hope). Then again i'm sure Reel DVD can do a few more things than Impression (maybe).

Compatability is based on a number of things. In no particular oreder:

1) The rate/ settings at which you encoded your movie to MPEG 2
2) The media you are writing to
3) The DVD authoring program
4) The DVD Player
5) The speed at which the disk was authored
6) The DVD writer.
....

Being that there is no one answer, many people find out what best suits them via trial and aware. Of course there are certain rules you can try and keep to.

there is no guarantee that all dvd authoring programs are creating a disc that is 100% legal to dvd specs.

and i think that the dvd specs don't exactly spell out every situation that you'll encounter in authoring a complex dvd.

we've all seen hollywood dvd's that don't work on a player or two that we have in the house, when most everything else plays fine on that player... and hollywood studios spend months using the best software there is to create those dvd's.